Static mixers are used in varied engineering applications for the continuous mixing, dispersing, reaction and/or heating and cooling of fluid materials. These devices are motionless (hence, “static”) and are typically used as in-line components that work through the energy of the flow stream in which they are employed. Static mixers may be used to treat liquids, gases and mixtures thereof with varying viscosities, volumetric flow rates and physical properties.
Conventional static mixers may comprise one or more mixing elements located within a tubular housing that is placed within the flow path that contains the fluid(s) to be mixed. For example, static mixers may comprise a unitary mixing element of a suitable shape, such as an elongated helical structure as described in U.S. Pat. No. 7,325,970, which is incorporated herein in its entirety for all purposes. In other examples, static mixers comprise individual mixing elements stacked in series at varying angles, such as the planar mixing elements described in U.S. Pat. No. 6,637,928, which is incorporated herein in its entirety for all purposes.
Static mixers are often used in high performance liquid chromatography (“HPLC”) applications. HPLC is a form of column chromatography in which a sample is placed within a solvent and pumped at high pressure through a column housing chromatographic packing material. The sample is carried by a moving carrier fluid stream such that compounds within the sample are separated and can thereafter be identified and quantified. HPLC often makes use of two or more different solvents in which the sample to be analyzed is injected. Because of the desired high precision of HPLC processes, the solvents must be thoroughly and homogenously mixed for maximum instrument performance. For example, incomplete solvent mixing may result in degradation of the HPLC chromatogram, in turn resulting in excessive baseline noise (as manifested by a periodic ripple of the detector signal versus time) and/or poor peak shapes (as manifested by broad and/or asymmetrical peak widths).